Balloon catheters are well known devices in which the catheter carries an inflatable balloon to occlude and seal a body space, to expand a blood vessel through pressurized inflation of the balloon or for other desired purposes which may typically be therapeutic procedures in the medical field.
An important characteristic of a dilation balloon catheter used for angioplasty is its profile, that is the outer diameter of the balloon when deflated. A low profile balloon is quite important and is usually attained by minimizing the dimensions of the core or inner tube where it extends through the balloon and by reducing the wall thickness of the balloon. The outer diameter effects the ease and ability of the dilation catheter to pass through a guide catheter through the coronary arteries and across a tight lesion. To reduce the outer diameter of the balloon in its deflated condition it is common to fold the balloon flat so that two wings or flaps are formed. These wings are then brought together so as to reduce the overall diameter of the deflated balloon. Commonly such configurations are achieved by installing a sleeve or balloon protector around the deflated balloon to bring the folds together. When inflation fluid is supplied to the folded balloon it causes the wings to unwrap so the balloon can inflate to its fully inflated configuration.
While reduction of profile is desirable it is also important to provide an inflated outer diameter of the balloon which is as large as possible relative to the deflated profile. When two wings are formed as the balloon is deflated they can be folded together to squeeze out the space between them without damaging the catheter during the procedure.
Commonly the wings of a balloon are folded or wrapped so they will return to a predetermined configuration when the balloon is deflated. Subsequent to inflation in an angioplasty procedure they will return to the formed configuration to enable easy withdrawal of the balloon from within the artery being treated. Reliance upon hand folded wings, however, can be fairly problematical because these wings do not necessarily conform to their original configuration upon deflation when they do not conform they may present a profile which is larger then necessary thereby possibly damaging the artery in which the catheter is inserted. Moreover when a catheter has to cross over several lesions or be used in several sites in the same procedure as in the case of a multi-vessel angioplasty, if the wings do not return to the predetermined configuration after evacuation of the inflation fluid the resultant deflated profile may compromise the ability to negotiate such vessels (or lesions). Moreover, abrasion can be increased together with the possible introduction of pin holes or wear spots.
The catheters for the medical procedure must be strong enough to withstand significant inflation pressures. They tend to be fairly stiff since the wall thickness must be sufficient to provide the necessary strength for these high pressures. Therefore when they are deflated, even if predetermined configurations are not introduced, they can flatten and lateral flat portions of the deflated balloon project laterally outwardly well beyond the rest of the catheter. It is undesirable to use balloons that have large, flat wings which may damage the artery wall as a deflated balloon is advanced through the arterial system into the desired position for inflation. Such flat wings can also interfere with the manipulation of the catheter and its easy advancement through the arterial system.